It is generally well known to provide ice making apparatuses (also referred to as "icemakers") for use in the freezer compartments of residential refrigerators. Examples of such icemakers are shown or otherwise disclosed in U.S. Pat. No. 5,212,955 to Hogan.
Icemakers such as known in the prior art use an aluminum ice mold as a structural member that provides mounting for separate elements such as an ice stripper and a water fill cup. These additional functions add mass and complexity which makes the ice mold one of the most expensive parts on the unit. In addition, the extra mass acts as a heat sink slowing temperature changes within the icemaker and slowing freezing and heating (for ice release).
Some prior art icemaker designs use separate molded fill cups to deliver water to the ice mold. However, the additional part adds material and labor cost to the product and adds assembly tolerance to the positioning of the water tube interface.
Some prior art designs also use separate molded ice strippers to remove the ice from the ejector after it has been swept from the ice mold. Ice strippers prevent the ice pieces from re-entering the ice mold. Such use of an additional part adds material and labor cost to the product and adds assembly tolerance to the positioning of the stripper.
In the current prior art, depending on brand and model, there are two distinct hole patterns for mounting the icemaker to the interior of the freezer, and different locations for the positioning of water fill tubes. This makes packaging of a single icemaker to fit all units difficult.
Some prior art icemakers also use a relatively complex circuit (see FIG. 7) which relies on double throw switches, and which has numerous connections. The circuit operates as follows (see FIG. 5 for state diagram):
1. A thermostat closes at a set temperature, beginning the cycle by energizing the heater and the motor.
2. A motor drives a cam which closes a "hold switch". The hold switch continues the cycle after the thermostat opens.
3. A cam operates a "full bucket detector arm" which doubles as a shutoff. The detector arm operates the shut off switch. The shut off switch opens during the eject cycle and remains open if the bucket is full, preventing the next cycle, otherwise it closes after a short interval. The hold switch continues the cycle.
4. The "water fill switch" is closed by the timer cam, but does not energize the valve because an alternate current path through the thermostat is available. This prevents a double fill.
5. The hold switch is opened by the cam after 360.degree. rotation, but the motor continues to run due to the closed thermostat.
6. The thermostat opens at the set temperature.
7. The shutoff switches open for a short interval.
8. The fill switch closes for the set time, energizing the water valve, filling the icemaker.
9. The hold switch opens, ending the cycle.
Most popular prior art icemakers available today use heat to release ice from the ice mold. The heating element typically used is a U-shaped tubular heater staked into a die cast ice mold. This type of element adds length to the unit (to provide for the U bend), adds material to the ice mold (for its mounting), requires high wattage (due to the mass and distance from ice), and tends to produce uneven heating. In addition, the tubular heater typically restricts the ice mold design to a die casting to allow mounting.
Prior art icemakers have arcuately shaped ice molds to provide ejection by means of a rotating arm which rotates about the center of the ice piece radius. The ice is formed in a die-cast aluminum mold body which has draft in the direction of die opening to allow ease of part removal. This draft in one direction creates an interference when the wider ice piece top rotates into the narrower bottom. More time and heat is required to melt the interference and eject the part. Prior art ice piece shapes tend to disadvantageously conform to the interior side of drinking glasses, creating a "damming" effect which is a nuisance to the consumer.
Prior art icemakers typically use a thermostat to detect completely frozen ice to start an ejection cycle. The thermostat is typically located on one end of the ice mold and attached by mechanical means such as screws and clamps. Good thermal coupling between the thermostat and the ice mold is essential to proper ice detection; therefore, a thermal paste is added between the parts. Some mounting schemes can allow some gaps or uneven pressure between the ice mold and the thermostat, causing premature cycling. The mechanical mounting means also require hardware and labor to attach the thermostat.
Prior art designs have used a gear-motor to drive a gear which attached to a cam to drive the ejector shaft. The rotating ejector shaft sweeps the ice out of its arcuately shaped mold and into the storage bin. The cam controls the time of the water fill by actuating a switch. The inherent gear mesh and cam fit-up tolerances can result in unacceptable water fill cycle tolerances. Excessive fill can lead to spillage or oversized ice pieces which will not fit through available ice dispensers.
Therefore, it may be seen that although the prior art has advantages, it likewise includes many disadvantages, not the least being a propensity towards complexity. As complexity tends to relate to high material, labor, and production costs, obviously there is a need to provide an icemaker which is simple in design and operation, yet suitable for use in the residential environment (e.g., reliable, and safe).